Bring a large pan of water to a boil, blanch the peas for a minute, then drain.
Set aside one-third of the peas and put the rest in a food processor with the chillies, preserved lemon, coriander leaves, oil, lemon zest, a third of a teaspoon of salt and plenty of pepper. Blitz to a rough paste.
Bring a large saucepan of well salted water to a boil, then cook the potatoes for 15 minutes, or until soft. Drain, transfer to a large bowl and roughly crush: you want at least a third of them left more or less whole.
Add the blitzed and whole peas to the bowl with the lemon juice and chopped coriander, gently stir through and serve warm